Modeling the Affects of High Powered Signals on the Civilian GPS User

Kirk R. Meyer

Abstract:	The civilian community uses the Global Positioning System (GPS) for precise 3-dimensional Position, Velocity, and Timing (PVT) information. The civilian user is becoming reliant upon GPS, and therefore system availability and accuracy are important. High-powered Mcode signals could potentially interfere with the civilian signals thereby decreasing availability and accuracy. This is an undesirable side effect that is currently being studied in more detail. The GPS Interference And Navigation Tool (GIANT) is capable of characterizing the effects of GPS jamming on various systems. It calculates the Signal to Noise (S/N) Ratios and position / timing errors for variations in transmitted signal strength and satellite antenna gain patterns. GIANT has been chosen as the modeling tool that will be used for analysis in this study. This study is set up in a 2020 timeframe where a fully functional GPSIII constellation is available. The constellation is composed of 27 satellites in 6-planes. Each satellite is equipped with a "spot beam" antenna for the M-code signal to use when high-powered signals are necessary. The satellite is capable of pointing (or steering) the "spot beam" antenna at any location on the earth. For example, up to 12 satellites have the ability to direct a concentrated beam of energy to a specific location on the earth. Using satellite ranges, angles of arrival, transmitted powers, and several other parameters, GIANT is able to calculate the strength of the desired signal at the receiver. GIANT then compares it to the level of the undesired signals. This comparison is used to determine the signal acquisition and tracking capabilities, along with timing / position errors. This study is being conducted to model the effects of several implementations of the high-powered M-code signal on the civilian user community. The M-code signal structure was designed so that very little power could “bleed” into the civilian Course Acquisition (C/A) frequency spectrum. Therefore, it is assumed that M-code signals will not affect the reliability of civilian signals. The study is seeking to validate this assumption and determine the next steps if / when it does not hold true.
Published in:	Proceedings of the 2004 National Technical Meeting of The Institute of Navigation January 26 - 28, 2004 The Catamaran Resort Hotel San Diego, CA
Pages:	287 - 293
Cite this article:	Meyer, Kirk R., "Modeling the Affects of High Powered Signals on the Civilian GPS User," Proceedings of the 2004 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 2004, pp. 287-293.
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